1. Field of the Invention
The invention relates generally to a method of administering a drug to an animal, such as cattle, swine, sheep and goats, and, more particularly, the invention relates to a method of subcutaneously injecting an antibiotic to an animal.
2. Brief Description of Related Technology
The injection of many antibiotics produces irritation and, potentially, illegal drug residues at the injection site of food-producing animals. Current cattle practice is oriented toward changing from an intramuscular injection of drugs and vaccines, which leaves both irritation and possibly drug residues in edible meat, to subcutaneous injection, which places those unwanted occurrences at the surface of the carcass in cattle. Because the hide of cattle is removed at slaughter, the injection sites are potentially visible and will be trimmed from the carcass. Even if that is not done, the edible meat is not damaged because the injection is not made into muscle. Nevertheless, even with subcutaneous administration, injection site irritation and potentially violative drug residues still remain on an edible portion of the carcass, namely the surface of the carcass itself.
Furthermore, any violative drug residues at the injection site cannot be monitored by current United States Department of Agriculture (USDA) inspectors, who require a “target tissue” for residue monitoring to homogeneously contain drug residues and always be readily identifiable to the layman. These target tissues are now defined as the kidney, liver, muscle and fat; and an injection site in any edible tissue, regardless of whether the injection is intramuscular or subcutaneous, fails the criteria for a target tissue because the injection site is not always readily identifiable, circumscript or homogenous with respect to drug residues.
The only alternative for antibiotics which have injection site residues, that are unacceptable as target tissues, is to use surrogate target tissue with which to monitor residue depletion. In that case, the surrogate target tissue is not the tissue in which potentially unsafe residues reside, but rather is the circumscript and/or homogeneous tissue (with respect to incurred drug residues) for which residues can be monitored until the time after drug administration at which all other drug residues in tissues decrease to safe levels. Because it is a surrogate target tissue, residues must decrease to a much lower concentration than those determined to be safe for that tissue from toxicological studies and food consumption values, in essence, penalizing that tissue's safe concentration because it is being used as a surrogate for the injection site.
Ceftiofur crystalline free acid sterile oil suspension (CCFA-SS) is a sustained-release ceftiofur product that provides for prolonged absorption from an injection site and thus affords a single injection treatment of bacterial diseases in animals. The prolonged absorption of the drug from the injection site makes the injection site contain the highest concentration of drug residues for the longest period of time (several weeks) during which time the concentration in all other tissues decreases to non-detectable levels. This makes the use of a surrogate target tissue impossible for this antibiotic. This is not unique to ceftiofur crystalline free acid, but rather is common to all sustained-release injectable compounds. Thus, one common alternative has been to utilize the surrogate tissue approach described above, as a result of injection site residues remaining with the edible carcass of food-producing animals. A more recent alternative has been to inject the antibiotic subcutaneously in the posterior of the ear of the animal, according to the teachings of commonly-assigned Brown U.S. Pat. No. 6,074,657 (Jun. 13, 2001).
International Patent Publication No. WO 94/20505 (Sep. 15, 1994), discloses CCFA, its preparation and a method of administration. The examples in that publication describe that cattle were administered CCFA by injection intramuscularly (IM) or subcutaneously (SC) either in or on the edible tissues of the animals. At page 10 of the publication it refers to antibiotics implants disclosed in U.S. Pat. No. 5,079,007 (Jan. 7, 1992) and to various pharmaceutical dosage forms exemplified in U.S. Pat. No. 4,902,683 (Feb. 20, 1990).
The administration by injection of an antimicrobial formulation (e.g., ceftiofur crystalline free acid sterile suspension) subcutaneously in the neck, flank, posterior of the ear, or other subcutaneous sites on the edible-tissue portions of the carcass for the treatment of bacterial diseases, such as bovine respiratory disease (BRD) and swine respiratory disease (SRD) is known. The subcutaneous aural (i.e., ear) administration of hormones as solid dose implants is known. Implants of antibiotics are known but are typically administered intramuscularly in the edible tissues of the food-producing animal. Small-volume vaccines have been administered successfully intradermally in the ear of dogs and swine. Also in swine, diagnostic allergens and a vaccine in small volumes have been administered subcutaneously in the dorsal part or the posterior side of the ear. Injection of ceftiofur crystalline free acid sterile suspension subcutaneously in the posterior of the ear has been disclosed.